Infall Motion

The inflow motion is measured. Figure 1.15 shows the isovelocity contours measured by the $^{13}$CO $J=1-0$ observation (Ohashi et al 1996). It should be noticed that the isovelocity lines run parallelly to the major axis. The north-eastern side shows a red-shift and the south-western side shows a blue-shift. Considering the configuration of the gas disk shown in Fig.1.14 (right), this pattern of isovelocity contours indicates not outflow but inflow. That is, the north-east side is a near side of the disk and the south-west side is a far side. Since a red-shifted motion is observed in the near side and a blue-shifted motion is observed in the far side, it should be concluded that the gas disk of the L1551 IRS5 is now infalling.

Figure 1.15: Isovelocity contours measured by the $^{13}$CO $J=1-0$ line. It should be noticed that the isovelocity lines run parallelly to the major axis. The north-eastern side shows a red-shift and the south-western side shows a blue-shift.